Intermediate mixing of thermal discharges into a uniform current     

John Eric Edinger  Edward M. Polk Jr. 《Water, air, and soil pollution》1971,1(1):7-31

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Florida manatees, Trichechus manatus latirostris, respond to approaching vessels     

Stephanie M Nowacek  Randall S Wells  Edward C.G Owen  Richard O Flamm 《Biological conservation》2004,119(4):517-523

Florida manatees inhabit shallow coastal and estuarine waters of the southeast US, a range that brings them into frequent contact with vessels. More than 30% of documented annual mortalities are attributed to vessel collisions, and most living animals bear the scars of multiple, non-lethal encounters. To document the behavior of manatees in the presence of vessels, we recorded their movements with an overhead video system. We scored six aspects of behavior during 170 vessel approaches, and compared their behavior with 187 control segments when no boats were present. Manatees in shallow waters and at the edge of the channel responded to approaches by orienting towards the nearest deep water, a boat channel, and increasing their swimming speed. Close boat approaches and shallow water depths exacerbated these responses. Our results indicate that manatees detect and respond to approaching vessels with an apparent flight response, a response which includes movement towards deeper water. If given sufficient time, i.e., approached or passed slowly, the manatees may then be able to reach deeper water and safe depths.  相似文献   

Tree plantations on farms: Evaluating growth and potential for success     

Jefferson S. Hall  Brian E. Love  Eva J. GarenJacob L. Slusser  Kristin SaltonstallShane Mathias  Michiel van BreugelDiogenes Ibarra  Edward W. BorkDean Spaner  Mark H. WishnieMark S. Ashton 《Forest Ecology and Management》2011,261(10):1675-1683

Interest in native species is growing across the tropics as reforestation of degraded lands becomes more widespread. In this study four tree species native to Panama - Cedrela odorata, Pachira quinata, Samanea saman, and Tabebuia rosea - were grown on rural farms at two dry tropical sites in Panama for up to five years. Survivorship and growth data at these “on-farm” trials are compared to data recorded from nearby experimental or “species selection” trial sites and evaluated in terms of soil fertility and management. Participant farmers were also asked about their interest in planting trees in general as well as their interest in 61 species grown in the species selection trial.Although, on-farm survivorship was variable and generally lower than that found on the species selection trial, one species (S. saman) experienced high and consistent survivorship. High survivorship combined with growth data from farms at both sites for this species suggests it would be a good candidate for extension projects working with rural farmers. Survivorship of other species appears more sensitive to farmer management and/or local site conditions. Generally lower growth on the Los Santos farms as compared to the species-selection trial is attributed to the lower soil fertility (plant available P) at the on-farm sites compared to the species selection trial. In contrast, only one species - P. quinata - had a growth variable found to be significantly lower between the on-farm and species selection trial sites in Rio Hato. C. odorata, P. quinata T. rosea can all be used in on-farm conditions with consideration to specific site and management conditions.By 2009, approximately 80% of the farmers planting trees still wished to participate in tree planting activities. All of the farmers no longer wishing to continue with the project expressed slow growth rates of trees as a principal reason. All but one of these farmers had growth rates for his/her trees markedly below those of the species selection trial nearby. Some farmers wishing to continue had very high mortality rates (>70% for all species), suggesting non-tangible benefits for participating in project activities. Other species that were not tested on-farm but grew well in the species-selection trials and were of interest to local farmers are discussed.As long as specific site and management conditions are carefully considered, data from species selection trials can be useful in informing tree planting projects with rural farmers; however, care should be taken to manage expectations.  相似文献   

果胶细菌诱导油菜结瘤与固氮研究     

胡小加 Cock.  EC 《植物营养与肥料学报》1997,3(3):275-279

果胶细菌处理油菜幼根（2天苗龄、根长3cm），同时接种紫云英根瘤菌突变菌株（Rhizobiumhuakuii），诱发类根瘤的结瘤率为96.80％。从这些类根瘤中分离的菌株能回接到原寄主。类根瘤的电镜观察可以明显地见到细胞内充满了细菌。乙炔还原法测定的固氨酶活性（C2H4）为76.80nmol／（planth）。  相似文献   

Evaluating the relationship between ecological and habitat conditions using hierarchical models     

Edward?L.?BooneEmail author  Keying?Ye  Eric?P.?Smith 《Journal of Agricultural, Biological & Environmental Statistics》2005,10(2):131-147

Understanding the relationship between an index of biological community state and habitat is important for policy makers and environmental managers. A common approach to modeling this relationship is to use regression. However, this simple method becomes complicated when the data are clustered and have both within-cluster and between-cluster spatial correlation. This article proposes a Bayesian hierarchical model that incorporates both types of spatial correlation. This model yields both an understanding of the within-cluster relationships as well as an overall relationship between these variables. We apply this method to evaluate the relationship between the index of biotic integrity (a common measure of fish condition) and the qualitative habitat evaluation index (a common measure of habitat quality). This method allows us to show that there is a relationship between the biological community state and habitat and that this relationship varies across river basins, while accounting for the within- and between-spatial correlations.  相似文献   

A comparison of three atrazine-degrading bacteria for soil bioremediation   总被引：3，自引：0，他引：3  

Edward Topp 《Biology and Fertility of Soils》2001,33(6):529-534

The ability of three atrazine-degrading bacteria, Pseudomonas sp. strain ADP, a Pseudaminobacter sp., and a Nocardioides sp., to degrade and mineralize this herbicide in a loam soil was evaluated in laboratory microcosms. These bacteria all hydrolytically dechlorinate atrazine, and degrade atrazine in pure culture with comparable specific activities. The Pseudaminobacter and Nocardioides can utilize atrazine as sole carbon and nitrogen source, whereas the Pseudomonas can utilize the compound only as a nitrogen source. The Pseudomonas and Pseudaminobacter mineralize the compound; the end product of atrazine metabolism by the Nocardioides is N-ethylammelide. At inoculum densities of 10⁵ cells/g soil, only the Pseudaminobacter and Nocardioides accelerated atrazine dissipation. The Pseudaminobacter mineralized atrazine rapidly and without a lag, whereas atrazine was mineralized in the Nocardioides-inoculated soil but only after a lag of several days. The Pseudaminobacter remained viable longer than did the Pseudomonas in soil. PCR analysis of recovered bacteria indicated that the genes atzA (atrazine chlorohydrolase) and atzB (hydroxyatrazine ethylaminohydrolase) were less stable in the Pseudaminobacter than the Pseudomonas. In summary, this study has revealed important differences in the ability of atrazine-hydrolyzing bacteria to degrade this compound in soil, and suggests that the ability to utilize atrazine as a carbon source is important to establish "enhanced degradation" by ecologically meaningful inoculum densities.  相似文献   

Microbial Reduction of Iodate     

Councell  Terry B.  Landa  Edward R.  Lovley  Derek R. 《Water, air, and soil pollution》1997,100(1-2):99-106

The different oxidation species of iodine have markedly different sorption properties. Hence, changes in iodine redox states can greatly affect the mobility of iodine in the environment. Although a major microbial role has been suggested in the past to account for these redox changes, little has been done to elucidate the responsible microorganisms or the mechanisms involved. In the work presented here, direct microbial reduction of iodate was demonstrated with anaerobic cell suspensions of the sulfate reducing bacterium Desulfovibrio desulfuricans which reduced 96% of an initial 100 µM iodate to iodide at pH 7 in 30 mM NaHCO₃ buffer, whereas anaerobic cell suspensions of the dissimilatory Fe(III)-reducing bacterium Shewanella putrefaciens were unable to reduce iodate in 30 mM NaHCO₃ buffer (pH 7). Both D. desulfuricans and S. putrefaciens were able to reduce iodate at pH 7 in 10 mM HEPES buffer. Both soluble ferrous iron and sulfide, as well as iron monosulfide (FeS) were shown to abiologically reduce iodate to iodide. These results indicate that ferric iron and/or sulfate reducing bacteria are capable of mediating both direct, enzymatic, as well as abiotic reduction of iodate in natural anaerobic environments. These microbially mediated reactions may be important factors in the fate and transport of¹²⁹ I in natural systems.  相似文献   

Factors affecting abundance of bowhead whales Balaena mysticetus in the eastern arctic of North America, 1915–1980     

Edward D. Mitchell  Randall R. Reeves 《Biological conservation》1982,22(1):59-78

The severely depleted bowhead whale Balaena mysticetus has failed to recover from overexploitation during the 18th and 19th centuries in the Eastern Arctic. Although commercial whaling for bowheads ended in this region about 1915, bowhead whaling by native people has continued until recently in parts of the Eastern Arctic. Low-level but persistent hunting by Inuit (Eskimos) may have inhibited bowhead population increase. Two natural mortality factors can be documented—ice entrapment and predation by killer whales Orcinus orca. There is little direct evidence of ice-related mortality but a strong circumstantial argument that ice conditions affect survival. Killer whales are known to prey on most species of large whales, and we believe bowhead whales and right whales Eubalaena glacialis are especially vulnerable. The bowhead's apparent failure to recover in the Eastern Arctic may be due to a combination of continued low-level hunting, habitat instability, and predation. Complete protection from all forms of hunting is necessary to ensure the bowhead's survival. Environmental disturbances due to industrial development in the Arctic may have direct and indirect impact on bowhead habitat and behaviour, creating an urgent need for further study.  相似文献   

Elemental and redox analysis of single bacterial cells by x-ray microbeam analysis     

Kemner KM  Kelly SD  Lai B  Maser J  O'loughlin EJ  Sholto-Douglas D  Cai Z  Schneegurt MA  Kulpa CF  Nealson KH 《Science (New York, N.Y.)》2004,306(5696):686-687

High-energy x-ray fluorescence measurements were used to make elemental maps and qualitative chemical analyses of individual Pseudomonas fluorescens strain NCIMB 11764 cells. Marked differences between planktonic and adhered cells were seen in the morphology, elemental composition, and sensitivity to Cr(VI) of hydrated cells at spatial scales of 150 nm. This technology can be applied to natural geomicrobiological systems.  相似文献   

Snowfall-driven growth in East Antarctic ice sheet mitigates recent sea-level rise   总被引：1，自引：0，他引：1  

Davis CH  Li Y  McConnell JR  Frey MM  Hanna E 《Science (New York, N.Y.)》2005,308(5730):1898-1901

Satellite radar altimetry measurements indicate that the East Antarctic ice-sheet interior north of 81.6 degrees S increased in mass by 45 +/- 7 billion metric tons per year from 1992 to 2003. Comparisons with contemporaneous meteorological model snowfall estimates suggest that the gain in mass was associated with increased precipitation. A gain of this magnitude is enough to slow sea-level rise by 0.12 +/- 0.02 millimeters per year.  相似文献